MEMS is a technology that exploits lithographic mass fabrication techniques of the kind that are used by the semiconductor industry in the manufacture of silicon integrated circuits. Generally the technology involves shaping a multilayer structure by sequentially depositing and shaping layers of a multilayer wafer that typically includes a plurality of polysilicon layers that are separated by layers of silicon oxide and silicon nitride. The shaping of individual layers is generally done by etching and the etching is generally controlled by masks that are patterned by photolithographic techniques. The technology also may involve the etching of intermediate sacrificial layers of the wafer to release overlying layers for use as thin elements that can be easily deformed or moved.
The technology has proven highly versatile and has been used to form a wide variety of miniature devices varying in size from millimeters to microns. MEMS technology is discussed in a paper entitled "MEMS The Word for Optical Beam Manipulation" published in Circuits and Devices, July 1997, pp. 11-18.
MEMS devices can be fabricated by the MCNC MEMS Technology Application Center, Research Triangle Park, N.C. 27709. The technology is described in "Multiuser MEMS Processes (MUMPS) Introduction and Design Rules," Rev. 4, Jul. 15, 1996 MCNC Mems Technology Applications Center, Research Triangle Park, N.C. 27709 by D. Keoster, R. Majedevan, A. Shishkoff, and K. Marcus.
Optical systems are becoming of increasing importance and optical switches have vital roles in many optical systems, particularly in optical networks that require rapid and flexible reconfiguration. Examples of such roles include protection switching of optical transmission links and the reconfiguration of optical cross-connects and add/drop modules (ADM) for wavelength division multiplexed (WDM) systems. There has been demonstrated a wide variety of optical switches even including several MEMS optical switches. Despite this wide variety, none has provided the combination of high optical performance, ultracompact size, low actuation voltage, and ultra-low power consumption with the potential of easy fabrication, low cost and suitability for use both in demanding gigabit optical networks and in cost-sensitive applications, such as fiber-to-the-home.
The present invention seeks to provide optical apparatus that helps satisfy this need.